Cavitation minimizer



Jan. 31, 1967- Filed July 6, 1965 FIG 4 FIG 5 D. M. BARDEN CAVITATIONMINIMIZER 2 Sheets-Sheet 2 gig ' DONALD M. BARDEN 60m Li /$22M ATTORNEYSUnited States Patent O 3,300,969 CAVITATIGN MHNIMEZER Donald M. Barden,Windsor, Vt., assignor to Bryant Chuclting Grinder Filed July 6, 1965,Ser. No. 469,524 8 Claims. (Cl. 60--52) This invention relates to asystem for controlling the flow of fluid to and from a double actinghydraulic motor.

The invention is particularly adapted to control a double actinghydraulic motor used to control sliding movement of a fixture on amachine. Under such conditions the sliding movement of a fixture buildsup a very considerable inertia force. It the rapid movement is stoppedabruptly by the blocking of fluid flow both to and from opposite sidesof the hydraulic motor, inertia forces cause excessive pressure to buildup in that side of the motor which normally returns to the reservoir,and simultaneously causes a marked decrease in the pressure in the otherside, or inlet side, of the hydraulic motor. Since there is a markeddecrease in pressure in the inlet side of the hydraulic motor cavitationoccurs which results in marked inefficiency of. the motor operation.

Accordingly, it is an object of this invention to provide means forminimizing the cavitation in a hydraulic system and provide for acushioned stop.

Accordingly, it is a further important object to prevent cavitation byproviding a flow of auxiliary fluid to the side of the hydraulic motorin which the pressure drops below a specified operating pressure afterthe hydraulic motor has been stopped by preventing the flow of fluid tothe motor.

With these and other objects in view, the invention consists of certainnovel features of construction, as will be more fully described andparticularly pointed out in the appended claims.

FIG. 1 and FlG. 2 show a typical circuit without a cavitation minimizer.

FIG. 3, FIG. 4 and FIG. 5 show a hydraulic circuit with a cavitationminimizer included.

FIG. 6 is a detail of valve A.

FlG. 'l and FIG. 2 show a typical hydraulic circuit without a cavitationminimizer. A volumetric pump PV delivers hydraulic fluid to the fluidmotor MP by way of line 8, valve A, and line 10. The return of hydraulicfluid to the reservoir R from the fluid motor MP is by way of line 12and valve A, and line 7. Valve A is controlled by a solenoid whichallows or restricts the flow of hydraulic fluid to the fiuid motor. Asshown in FIG. 1 fluid is pumped by volumetric pump PV when solenoid SOLS1 is energized allowing fluid to enter line 10 through fluid motor MFto turn in the direction shown, and returning to reservoir R by way oflines 12 and 7. When solenoid SOL S1 is deenergized, as shown in FIG. 2,the flow is stopped. However, due to the high inertia momentum of thedriven parts the motor MF maintains its rotation thereby providing anexcessive pressure in line 12 and a simultaneous decrease of pressure inline 10. This decrease of pressure in line 10 causes a cavitation condition which is very detrimental to the motor.

Normally, a relief valve is inserted between the inlet and exhaust linesto allow the fluid to enter the line having the decreased fluidpressure. The drawback to the relief valve is that it is actuated whenthe pressure reaches a predetermined pressure, and often times reactstoo late to prevent cavitation effects to the inlet side of the system.

in other words, there is a Certain interval when fluid should bebypassed into the inlet side of the motor to overcome the cavitationeffects, but because of the comparatively slow action of the reliefvalve cavitation efiects originate in the inlet side before the reliefvalve can supply enough fluid to it.

Patented Jan. 31, 1967 To overcome the inadequacy of a relief valveinserted between the inlet and exhaust a cavitation minimizer isinserted between the exhaust and inlet side of the fluid motor. As shownin FIGS. 3, 4, and 5, the cavitation minimizer consists of a cylinder 2having a slidably movable piston 4 adapted to slide from one endposition of the chamber 3 of the cylinder to the other end. A line 14 isconnected at 11 to line 10 and is connected to port 15 of. cylinder 2.Another line 16 is connected at 13 to line 12 and is connected to port17 of cylinder 2. The lines 14 and 16 include restriction valves V1 andV3 respec tively to provide regulatory flow to and from the chamber 3 ofcylinder 2 Also connected to the line 10 at 19 is another line 18. Line18 is connected to the end port 20 of cylinder 2. The line 18 includes arestriction valve V2 to allow for restrictive flow between the line 10and cylinder 2. A line 26 is connected to line 18 for the purpose ofby-passing valve V2 and includes a relief check valve 30.

Similarly line 22 is connected at 23 between line 12 and end port 24 ofcylinder 2 and includes a restriction valve V4 to allow for restrictiveflow between the lines 12 and cylinder 2. A by-pass line 28 is connectedto line 22 for by-passing valve V4 and includes a relief check valve 32.

Check valves 30 and 32 are unidirectional flow valves and allow fluid toflow only in one direction,

Restriction valves V1, V2, V3, and V4 are regulatory valves and areadapted to be adjusted to provide for fluid to be regulated properly toallow for the piston 4 to travel in the chamber 3 of cylinder 2 from oneend position to the other at a predetermined rate of speed.

A line 38 is connected to lines 10 and 12 at 11 and 13 respectively andis connected to the reservoir R. However, a check valve 34 is placednear the connection 11, and a check valve 36 is placed near theconnection 13. The check valves 34 and 36 allow for prevention of fluidflow to the reservoir when the fluid motor MP is being driven in onedirection. However, at the time of stopping the rotation of motor MP,the valve connected to the line having the decreased pressure allowsfluid from the reservoir to flow into the line decreasing the cavitationeffects.

The device operates in the following manner:

(I) When solenoid SOL S1 is energized, the valve A allows flow ofhydraulic .fluid from pump PV to the inlet side of fluid motor MF bymeans of lines 8 and lit. The flow of fluid in line v10 passes throughlines 14 and 18 through restriction valves V1 and V2 and through checkvalve 30 without restriction to slidably move free floating piston 4 inchamber 3 of cylinder 2 to a position shown in FIG. 3. The fluid motorMP is thereby adapted to rotate in a direction shown in FIG. 3. At thistime flow of fluid from the lines It) and 12 is restricted from enteringthe reservoir by means of check valves 34 and 36 since the pressure isgreater in lines 10 and 12 than line 38.

(II) When solenoid SOL S1 is de-energized, the valve A prevents the flowof fluid from pump PV to the fluid motor MF. Due to the inertia force ofthe fluid and motor, the motor MP continues to maintain its rotationaldirection (see FIG. 4) thereby causing excessive pressure in line 12 andsimultaneously causing a decrease in pressure in line 10. Thesimultaneous decrease in pressure in line 10, which causes a partialvacuum, and the increase in pressure in line 12 forces piston 4 toimmediately move in the chamber of cylinder 2 to a position shown inFIG. 4. That is the fluid flows from line 12 through connection 23, intoline 22, through relief check valve 32 and restriction valve V4 intocylinder 2 by means of end port 24.

The force of fluid flow moves the piston toward the right, as shown inFIG. 4, causing the fluid that was in the chamber 3 of cylinder 2 toexhaust into the line by means of lines i4 and 13. Line 14 receives mostof the primary fluid through port 15 and is adapted to replenish line10.

In the position shown in FIG. 4, the port 15 is shut oll from furtherfluid flow, however, fluid continues to flow into line 10 through line18 by means of end port 20. Additional fluid is allowed to enter line10, if necessary by means of check valve 34 which accumulativelyprevents cavitation eflects in line 10.

(III) When solenoid SOL S2 is energized, fluid from pump PV enters linel2, thereby causing fluid motor MF to then reverse direction. The flowof fluid in line 12 concurrently enters line 22, and enters cylinder 2by means of end port 24, to move piston 4 toward the extreme endposition of chamber 3 as shown in FIG. 5. After the piston 4 moves pastthe port 17, additional fluid is allowed to enter the chamber ofcylinder 2 by means of line 16.

As disclosed hereinabove, the fluid motor MP is adapted to be stoppedand rotated in opposite directions with out cavitation eflects in theinlet sides of the system.

FIG. 6 shows a modification of the cylinder thus far described with thearrangement similar to the parts of the embodiment of FIGS. 3 through 5.and marked with the same reference numerals followed by the small letterb. Included in the cylinder 2!) are a plurality of ringed annularrecesses or chambers, such as shown, at each end of the cylinder. Theringed annular recess 40 is connected directly to port 17!), as isringed annular recess 46 connected to port 15b, for the purpose asdescribed hereinabove in the preferred embodiment. The ports 15b, 171)are located inwardly from each end of the cylinder substantially nearthe midpoint thereof. However, ringed annular recesses 42 and 44 areconnected to the port 17b by means of a threaded bore 4i. Similarlyringed annular recesses 48 and 5% allow fluid to flow to port 15bthrough bore 47. Plugs 43, 45, 49 and 51 secure the openings that leadto the ringed annular recesses 42, 44, 4S and 50 respectively. Theadjustable screws 52 and 54 allow for a differential rate of flow fromthe chamber 3/2 of. cylinder 21) by means of adjusting the screws toaccommodate for a greater amount of fluid flow to lines 101) and 1211,respectively. The threaded bores 41 and 47 are in close engagement withthe threaded screws 54 and 52 respectively, so that the screws areadjustable to prevent the flow of fluid. The threaded hole is tappedthrough the ringed annular recesses or chambers, and consequently, ifthe screw is backed off so that it does not enter any of the chambers orringed annular recesses the ports 17b, 15b receive all the fluid fromthe chamber. If the screw is adjusted so that it passes the ringedannular recess 44 and enters the threaded portion between ringed annularrecesses 44 and 42, the annular recess 44 is cut off from connectionwith annular recess 42. Likewise, as the screw is turned until itencroaches on ringed annular recess 42 and enters the threaded portionbetween 42 and 40, it eflectively eliminates annular recess 42 as one ofthe passages for the fluid and leaves only annular recess 40 to handlethe fluid flow. In other Words, as the screw is adjusted inwardly thereis a shortening of the length of the cylinder through which the pistontravels before cutting off the outlet at 17b. Beyond this point, thefluid must flow out of 24b alone at a much reduced rate of flow due torestriction valve V4b. The reason for the greater flow is quite evident,in that at the instant the fluid flow is blocked by the valve, inertiaforces cause an increase in pressure in the outlet side of the fluidmotor, thereby causing the piston 4b to slidably move toward the otherend of the chamber of the cylinder. Depending upon the adjustment of thescrews 52, 54, a quantity of fluid is delivered to the inlet side of thefluid motor system causing an immediate decrease in cavitation effects.As the piston slides further toward the end position in the chamber ofthe cylinder, fluid flow is progressively reduced until piston 4b movespast the ringed annular recesses thereby closing ofl all flow of. fluidthrough the ports 15b or 1711. Thereafter, the flow of fluid is forcedthrough line 18/) or 22/). The rate of flow must be decreasedprogressively in steps, otherwise the fluid motor will continue rotatingin the same direction for too long a period of time, and stopping therotation will not be accomplished properly. In other words, if thecavitation minimiZer replenishes the inlet side of the line to the motorat too rapid a speed, although the cavitation effects will bedissipated, the motor will continue to totate in the same direction asoriginated, and will not slow down as intended. Therefore, a combinationof allowing enough fluid to prevent cavitation and to dccrease therotation of the motor in progressive cps in as short a time as necessaryis needed. This is accomplished by the aforesaid description.

While in the foregoing description the invention was explained inconnection with one possible form or cmbodiment thereof whereforecertain specific terminology and language have been used herein, it isto be understood that the present disclosure illustrative rather thanrestrictive and that changes and modifications may be resorted towithout departing from the spirit of the invention as defined by theclaims which follow.

What is claimed is:

1. A system for controlling the operation of a fluid actuated motorcomprising;

a fluid actuated motor;

a fluid reservoir;

a volumetric pump;

a fluid supply line and a fluid return line connecting said reservoir,said pump and said motor;

valve means connected between said motor and said pump and reservoir forcontrolling the flow of fluid to and from said motor;

a fluid cylinder connected between said fluid supply line and said fluidreturn line, said fluid cylinder including;

a chamber;

a free floating slidably movable piston in said chamber;

plurality of port means on said cylinder connecting said chamber of saidcylinder and said fluid supply line and said fluid return line,respectively; whereby fluid in said chamber on one side of said pistonis forced into said fluid supply line to control cavitation defects whensaid controlling valve means prevents flow of fluid to said motor.

2. A system as defined in claim 1, wherein said cylincomprises;

a plurality of ringed annular recesses, each of said ringed annularrecesses having a diameter larger than the diameter of said bore of saidcylinder;

and an adjusting means for controlling the flow of said fluid throughsaid ringed annular recesses through said porting means to either saidfluid supply line or said fluid return line when said valve means forcontrolling said flow of fluid to said motor is discontinued therebyminimizing cavitation.

3. A system as defined in claim ll wherein said cylinder comprises aplurality of ringed annular recesses, each of. said ringed annularrecesses having larger diameters than the diameter of said bore, atleast one of said ringed annular recesses connected to a means forporting said fluid, and an adjusting means for controlling the flow ofsaid fluid through said ringed annular recesses through said portingmeans to said fluid supply and said fluid return lines.

4. A system as defined in claim 3 wherein said adjusting means comprisesa screw adapted to control fluid flow from said cylinder to said fluidsupply and said fluid return lines.

5. A system for controlling the operation of a fluid actuated motorcomprising; a fluid motor, a fluid reservoir, a volumetric pump, a fluidsupply line and a fluid return line connecting said fluid motor and saidfluid reservoir, means for controlling the flow of fluid to and fromsaid fluid motor, an hydraulic cylinder, said cylinder having a chambertherein, a free floating piston slidably movable in said chamber of saidcylinder, a plurality of cylinder port means connected to said cylindersubstantially near the midpoint thereof, a first line connecting saidfluid supply line to one of said plurality of cylinder port means, asecond line connecting said fluid return line to the other of saidplurality of cylinder port means, whereby movement of said piston isadapted to force fluid from the chamber of said cylinder into said fluidsupply line when said controlling means prevents further flow of fluid.

6. A system as defined in claim further including a line connecting saidfluid supply line and said fluid return line to said fluid reservoir,said line having a valve controlling the flow of fluid near eachconnection of said line to said fluid supply line and said fluid returnline.

7. A system as defined in claim 4 further comprising a threaded boreadjacent said ringed recesses and said port means, whereby saidadjusting screw is adapted to be threadedly movable within said threadedbore to provide for adjustment of fluid flow from said cylinder.

8. A cylinder comprising:

a stationary housing having a substantially cylindrical boretherethrough defining a chamber therein;

a first port means on one end of said housing connected to said chamberfor admitting pressure fluid into said chamber;

a second port means on the other end of said housing connected to saidchamber for admitting pressure fluid into said chamber;

a piston in said cylindrical bore adapted to be slidably movable withinsaid chamber;

a first set of ringed annular recesses integral with one end of saidhousing and having its diameter larger than said bore of said chamber;

a second set of ringed annular recesses integral with the other end ofsaid housing and having its diameter larger than said bore of saidchamber;

a third port means connected to said cylinder housing near the midpointthereof and to said first set of said ringed annular recesses;

a fourth port means connected to said cylinder housing near the midpointthereof and to said second set of said ringed annular recesses;

adjusting means connected to each of said first set and said second setof said annular recesses respectively;

whereby fluid on one side of said piston is adapted to exit from saidchamber through said port means at one end of said housing andadjustably through said port means connected to said ringed annularrecesses near the midpoint of said cylinder housing.

References Cited by the Examiner UNITED STATES PATENTS 2,890,683 6/1959Pilch -52 X 3,233,409 2/1966 eis 60-53 X 3,262,467 7/1966 Stacey.

EDGAR W. GEOGHEGAN, Primary Examiner.

1. A SYSTEM FOR CONTROLLING THE OPERATION OF A FLUID ACTUATED MOTORCOMPRISING; A FLUID ACTUATED MOTOR; A FLUID RESERVOIR; A VOLUMETRICPUMP; A FLUID SUPPLY LINE AND A FLUID RETURN LINE CONNECTING SAIDRESERVOIR, SAID PUMP AND SAID MOTOR; VALVE MEANS CONNECTED BETWEEN SAIDMOTOR AND SAID PUMP AND RESERVOIR FOR CONTROLLING THE FLOW OF FLUID TOAND FROM SAID MOTOR; A FLUID CYLINDER CONNECTED BETWEEN SAID FLUIDSUPPLY LINE AND SAID FLUID RETURN LINE, SAID FLUID CYLINDER INCLUDING; ACHAMBER; A FREE FLOATING SLIDABLY MOVABLE PISTON IN SAID CHAMBER; APLURALITY OF PORT MEANS ON SAID CYLINDER CONNECTING SAID CHAMBER OF SAIDCYLINDER AND SAID FLUID SUPPLY LINE AND SAID FLUID RETURN LINE,RESPECTIVELY; WHEREBY FLUID IN SAID CHAMBER ON ONE SIDE OF SAID PISTONIS FORCED INTO SAID FLUID SUPPLY LINE TO CONTROL CAVITATION DEFECTS WHENSAID CONTROLLING VALVE MEANS PREVENTS FLOW OF FLUID TO SAID MOTOR.